I just tried to put a gtx 970 in a system with a 1070 and the system refused to show me even the BIOS. I have read online that Nvidia restricts newer gen cards from running in the same system as one another. Is this true?

To test this theory I tried installing a 1060 in the system with the 1070 and everything worked fine. Can anyone else confirm or disprove this?

Shouldn't. I've run 980Ti with 2 1080Tis and didn't have a problem.

I had gtx960 and gtx1070 working fine together for a long time. If hardware problems are ruled out, I would suggest trying pre-RTX Nvidia drivers (anything under version number 400 I believe) and see if it works.

I ran a Wow contest machine this August with a 1060 and 970 with no issues.

Did you reinstall the drivers after adding the second card? That is needed for the drivers to pick up the additional card.

Do you have a bad PCIe slot? Try the cards in different slots. Swap them around.

I've mixed Pascal and Maxwell and plenty of others have as well. Video out at BIOS may only come from one card/iGPU though.

So far I've tried every card swap combination possible and I can't get it to show anything on screen. It only works with the 1060 and 1070. I am on a pre 400 series driver too.

So far I've tried every card swap combination possible and I can't get it to show anything on screen. It only works with the 1060 and 1070. I am on a pre 400 series driver too.

If you can't even get to the BIOS screens. You've probably tried most of this but...

1) Flash the latest MB BIOS.
2) Try the monitor output from every connection on both GPUs. The live output often changes when you add cards.
3) Try the same setup in different computers. Try the GPUs in different PCIe slots.
4) Make sure that you have an adequate power supply to drive 2 power hungry GPUs.
5) Make sure that the GPUs are firmly clicked down into the slots.

If you still can't get to the BIOS when the 970 card is inserted, then there's probably a problem with the GPU. I see that you can use it singly in a system. See if there's a new GPU BIOS and if so flash it. Call the GPU manufacturer for their advice. If you still can't get it to work with other cards, you may be stuck using it in a system by itself. You could also sell it with the disclaimer that it must be used as the only GPU in a system. Best of luck. Let us know how it goes.

Some of the more recent graphics cards are designed to allow running them if the motherboard uses a UEFI, but not if it uses a BIOS instead. Also, some have a switch to tell them whether to allow running with a UEFI or with a BIOS instead.

Not all graphics card companies make the same choices of which to make available, so finding that a particular model of GTX 970 has one of these choices does not mean that every model of GTX 970 has the same choice.

A BIOS and a UEFI perform about the same function, but a UEFI allows graphics cards to provide their own piece of UEFI rather than relying on the one for the motherboard to know how to handle all possible choices of what graphics board to use.

You may need to check the specs for your graphics card and your motherboard to make sure that both are set to use a BIOS, or both are set to use a UEFI instead.

Some of the more recent graphics cards are designed to allow running them if the motherboard uses a UEFI, but not if it uses a BIOS instead. Also, some have a switch to tell them whether to allow running with a UEFI or with a BIOS instead.

Not all graphics card companies make the same choices of which to make available, so finding that a particular model of GTX 970 has one of these choices does not mean that every model of GTX 970 has the same choice.

A BIOS and a UEFI perform about the same function, but a UEFI allows graphics cards to provide their own piece of UEFI rather than relying on the one for the motherboard to know how to handle all possible choices of what graphics board to use.

You may need to check the specs for your graphics card and your motherboard to make sure that both are set to use a BIOS, or both are set to use a UEFI instead.

I ran into this on some newer NVidia cards and an older Biostar MB. Luckily Biostar had a MB BIOS update, so check your MB support site.